The present invention relates to a digital camera having an image capturing element, and specifically to a digital camera having a vibration reduction system.
In recent years, the number of pixels in an image capturing element for a digital camera has been increased, for example up to six million, or more. As the number of the pixels increased, a pixel pitch in the image capturing element has been narrowed. With such an image capturing element, when an ISO sensitivity of the image capturing element is lowered, a captured image is often blurred by hand movements of a user specifically when the image is captured using a telephoto lens. In order to prevent such an image from becoming blurred, an example of a technique for a digital camera to reduce vibration caused by such hand movements is disclosed in Japanese Patent Provisional Publication No. P2001-245199which discloses a digital camera to detect the vibration and compensate the vibration by driving the image capturing element horizontally and vertically in directions of the vibration detected for an amount corresponding to the vibration. In the disclosure, no specific configuration to drive the image capturing element is disclosed, however, for example a movable table to have the image capturing element thereon that can be driven in an X direction (i.e., horizontally) and a Y direction (i.e., vertically) respectively may be employed. For another example, a parallel wire mechanism, which is generally employed in an optical head of an optical disk device, with four resilient wires to movably support the image capturing element may be employed. Further, a drive mechanism with a ball screw, which is adapted to drive the image capturing element by using rotary force of a rotary drive source such as a voice coil motor, a DC (direct current) motor, and a step motor, may be employed. The drive mechanism with the ball screw may be also employed to drive one of a plurality of lenses in a photographing lens unit of a camera horizontally and vertically. An example of such camera is disclosed in Japanese Patent Provisional Publication No. 2003-84328.
However, each of the above-described drive mechanisms contains a problem. The movable table requires a plurality of guide bars and a table itself, which take space and prevent the camera from being downsized. In the parallel wire mechanism, the image capturing element supported by the resilient wires is often misaligned in a direction of an optical axis by a small amount, when the resilient wires are deformed to drive the image capturing element, thus an image captured may not be properly focused. Specifically, when a lens that allows more quantity of light to pass through with an aperture value for example f/1.4 is used, the blur of the image may be apparent and recognized by the user. In the ball screw mechanism, the image capturing element cannot be driven by a large amount with respect to a rotation angle of the motor, therefore the image capturing element may not be driven speedily enough to compensate the vibration.